The present invention relates generally to a triangulation position detection method and device for detecting the presence of an object within a predetermined target window using light radiation. More specifically, the invention is applied to a dispenser, such as a beverage and/or ice dispenser.
Generally, a beverage and ice dispenser consists of a mechanical push rod closing an electric switch or a manually operated push-button electric switch which actuates a dispenser to dispense product. It is thought that such dispensers transmit communicable diseases. For example, a person with such a disease who drinks out of a cup and returns to the dispenser to refill the cup must contact the cup to the dispensing push rod such that germs may be transferred from the cup to the push rod wherein the next individual to use the mechanical dispenser may come in contact with the germs by drinking from a cup subsequently placed against the same push rod.
Heat sensing devices which are typically used for activating water faucets in response to sensing heat generated by the operator's hand within a certain proximity of the faucet are not very accurate in determining position because of their temperature dependency. Heat sensing devices are activated when an object of a given temperature is at a certain proximity to the heat sensing device. However, if the temperature is lower than the temperature expected at the given proximity, the device will not be activated until the object with lower temperature is brought closer to the heat sensing device which shortens the expected proximity. In other words, an object's distance from the heat sensing device, to activate the device, will vary with temperature and therefore will not give precise and predictable results.
Another type of position sensing device is a light beam interrupter system in which a beam of infrared light is transmitted to a photodetector mounted opposite the infrared transmitter which transmits a steady light beam and wherein the interruption of the light beam indicates the presence of an object therebetween. For example, see U.S. Pat. No. 4,822,996 issued to Lind. This type of system is only capable of determining whether an object is present between the transmitter and the receiver and not the proximity or position of an object. In other words, this type of a detector would only function on a single axis.
An alternative transmitter and receiver arrangement was provided by Hosel, U.S. Pat. No. 5,002,102 which emits a steady beam of light from a transmitter which is reflected back to a receiver mounted adjacent the transmitter. The Hosel system requires a microcomputer with a microprocessor for calculating a distance between the transmitter/receiver and the fill level in a bin-the distance being an inverse function of the intensity of the light beam. The Hosel apparatus is based on direct reflection, that is, it simply emits light and determines how much is returned to determine the fill level distance and is therefore limited to detection on a single axis, and unless confined within a closed system such as the fiber storing bin disclosed by Hosel, the Hosel device would be susceptible to stray light sources and be inoperative in the presence of such stray light sources.
The main disadvantage of these prior systems is that they are limited to detection on a single axis and therefore are not true position detection devices. In other words, a light beam interrupter system, for example Lind U.S. Pat. No. 4,822,996, detects an interruption in the light beam anywhere in the linear axis defined to extend from the light emitting source to the light receiving detector, and cannot differentiate the position of the interruption along that linear axis. A heat sensing device may be able to detect on multiple axes, but unless the temperature of the intruding object is constant, the point of detection varies with the temperature of the object, and therefore true position detection cannot be achieved.